1. Field of the Invention
The present invention relates to a method of processing a substrate, a method of manufacturing a solid-state imaging device, a method of manufacturing a thin film device, and programs for implementing the methods, and more particularly to a method of processing a substrate in which an insulating film is polished by chemical mechanical polishing.
2. Description of the Related Art
A color resist method is particularly widely used as a method of manufacturing color filters in electronic devices, for example solid-state imaging devices such as CCD sensors.
In the formation of the color filters, for example in the case that green, red, and blue color filters are formed in this order, the subsequently formed red and blue color filters are affected by the previously formed color filter so that a gradient arises in the film thickness. It is thus difficult to form the color filters to a desired film thickness, i.e. there has been a lack of film thickness controllability. Moreover, variation may arise in the color filter film thickness within a single linear sensor or between multiply demarcated linear sensors, and for solid-state imaging devices this has been a cause of the uniformity of the color filter film thickness on a macroscopic scale becoming poor, and noise and sensitivity irregularity arising, bring about a marked degradation in the line sensor characteristics.
To solve the above problem, hitherto there has been disclosed a color filter manufacturing method in which the film thickness of second and third color filters giving second and third colors is made to be not less than 1.3 times the film thickness of a first color filter giving a first color, whereby no gradient arises in the film thickness of the second and third color filters within an effective pixel, and hence even there is overlap with the first color filter at a peripheral edge portion of each pixel, the occurrence of a difference in film thickness between the portion where there is this overlap and a central portion of the pixel can be suppressed (see, for example, Japanese Laid-open Patent Publication (Kokai) No. 2004-311557).
However, in recent years, for solid-state imaging devices, the pixel size has been reduced as the number of pixels has been increased, and hence art for making the color filter array finer has become essential. Moreover, as the pixel size has been reduced, making the color filters be thin films has also become essential for increasing the light collecting ability of a solid-state imaging device.
With the conventional color filter manufacturing method described above, the color filter array segmentation is carried out assuming a line width of 10 μm. Carrying out the color filter array segmentation to a line width of, for example, not more than 1 μm is thus structurally difficult, and hence increasing the solid-state imaging device fineness has been difficult.
With the color resist method, it has been known from hitherto that to make the color filters be thin films, it is effective to make the percentage content of the colorant relative to the photosensitive resin composition in a colorant-containing photosensitive resin composition that is coated on as high as possible.
However, if the percentage content of a dye as the colorant is made to be close to 50%, then although a desired pattern shape can be obtained through exposure and development, thermal curing of the resin composition becomes difficult. The color filters must be resistant to a solvent contained in each resin composition, and in the conventional manufacturing method, each of the color filters is given such solvent resistance by thermally curing the corresponding resin composition. However, if thermal curing of the resin composition is not carried out, then the solvent resistance of the resulting color filter will be poor, and hence it will become impossible to coat on a resin composition for forming a color filter of another color in a subsequent step. Moreover, to give sufficient solvent resistance, if the thermal curing is carried out at a higher temperature (e.g. not less than 200° C.), the color filters may undergo reflow, or the dye may be chemically changed by the heat, resulting in the color filters no longer exhibiting their original spectral characteristics.
To solve the above problem, there has been disclosed a color filter manufacturing method in which a resin composition is coated on to form color filters, and then a protective film that is an insulating film such as a silicon oxide (SiO2) film or the like is formed on each of the color filters (see, for example, Japanese Laid-open Patent Publication (Kokai) No. 2003-75625). As a result, even if the resin composition coating film is not thermally cured through high-temperature heat treatment, the solvent resistance of the color filters can be made high through the presence of the protective film, and moreover because high-temperature heat treatment is not carried out, the percentage content of a colorant in the color filters can be made high, and hence the color filters can be made thin.
However, in the above color filter manufacturing method, although the color filters can be made thin, a low-temperature plasma CVD step is required to form an approximately 50 nm-thick SiO2 layer as the protective film on the color filters, and hence there has been a problem that the manufacturing time (TAT) is increased.
Moreover, in the conventional color filter manufacturing method, photodecomposition (bleaching) of an unwanted photosensitizer or the like is carried out by irradiating the resin composition that has been coated on with ultraviolet radiation, and then the resin composition is thermally cured through heat treatment. However, controlling the percentage shrinkage of the resin composition due to the thermal curing is difficult, and hence an error in the color filter film thickness arises each time the heat treatment is carried out. The error in the color filter film thickness causes optical axis misalignment in the solid-state imaging device, and thus causes color irregularity or image irregularity to arise.
Moreover, in some conventional solid-state imaging devices, microlenses are provided via a protective film on color filters formed on a flattening film which is an insulating film. In the case that the distance from each light-receiving portion (photoelectric transducer) to the corresponding microlens is great, i.e. the case that the layers between the photoelectric transducer and the microlens are thick, diagonally incident light is blocked by protrusions formed by electrodes and so on, bringing about a decrease in the light collecting ability of the solid-state imaging device. It is thus required to make the layers between the photoelectric transducers and the microlenses thin. Meanwhile, there are demands to improve the image quality with regard to screen hues, and accompanying this it is necessary to further improve the quality with regard to the transmitted color spectral characteristics of the color filters. It is thus necessary to strive to improve the quality of the hues, which can be done by making the color filters thicker. However, making the color filters thicker goes against the requirement to make the color filters be thin films described above.
Furthermore, due to the fineness of solid-state imaging devices being increased, when forming a solid-state imaging device, there have come to be strong demands in a step of forming upper layer elements such as the color filters and microlenses on the precision of alignment of the upper layer elements to base elements. This alignment of the upper layer elements to the base elements is carried out by detecting via the flattening film reflected/diffracted laser light from alignment marks formed on the base elements. However, when detecting the position of the image formed of such an alignment mark via a thick flattening film or protective film, much optical shifting is prone to taking place. To improve the precision of the alignment between the base elements and the upper layer elements, there are thus again demands to make the flattening film and protective film be thin.
To achieve the above, one can envisage making the flattening film and protective film thin, thus reducing the thickness between the photoelectric transducers and the microlenses. As a method of making the flattening film or protective film thin, one can envisage a method in which the flattening film or protective film is formed by etch back.
However, in the case of carrying out etch back, with an etching method using plasma, the etched surface and the electronic device are damaged, and a difference in charge between light-sensitive portions and transfer portions of the solid-state imaging device is brought about, causing an increase in the dark current output. Moreover, if wet etching is used, then controlling the amount removed of the flattening film or protective film is difficult, and hence there has been a problem that the desired film thickness cannot be obtained. In this way, with a conventional substrate processing method, it has been difficult to form a flattening film or protective film of a desired film thickness without damaging the electronic device.